1. Field of the Invention
The present invention relates to a liquid ejection head applied to a printing apparatus that ejects liquid such as ink to perform printing and to a method for fabricating the same.
2. Description of the Related Art
Liquid ejection printing apparatuses (hereinafter also simply referred to as printing apparatuses) are widely used as output devices or the like for computers and a wide variety of printing apparatuses are being produced on a commercial basis. Printing methods for such printing apparatuses include a method that uses an electrothermal transducer as an ejection energy generator. A liquid ejection head built in a printing apparatus that uses the method has an electrothermal transducer provided in a pressurizing chamber of a print element substrate and an electrical pulse which serves as an ejection signal is applied to the transducer to provide thermal energy to liquid such as ink, and uses bubble pressure generated in boiling of the liquid to eject the liquid.
In a liquid ejection head used for such a liquid ejection printing apparatus, a plurality of print element substrates is arrayed and bonded to a base plate. In order to precisely dispose the respective print element substrates, reference marks are provided on the print element substrates and the reference marks are optically photographed and recognized for alignment. In the alignment, the print element substrate is sucked onto a vacuum finger (hereinafter also simply referred to as a finger) and photographed from above with two CCD cameras. The reference mark includes a circular portion and four rectangular portions, all of which are used as one mark.
While increasing a photographing magnification ratio of the optical system is effective for more accurately disposing the plurality of print element substrates, the increase of the photographing magnification ratio could cause the following problems.
In the case where the photographing magnification ratio of the optical system is increased in order to perform more accurate alignment, the photographing region becomes narrow accordingly. Furthermore, variations in the outside dimensions of the print element substrates and variations in stop precision of the print element substrate transport system before the print element substrates are sucked onto the finger cause variations also in the relative positional relationship between the finger and the reference marks provided on the print element substrates.
For this reason, in the case where the photographing region narrows at the first photographing after a print element substrate is sucked onto the finger, a reference mark does not exist in the photographing region, which may disable alignment of the print element substrate.
Furthermore, even in the case where the photographing magnification ratio is increased and the rectangular portions of the reference mark are included in the photographing region, it takes long time to perform alignment of the print element substrate because the direction in which the circular portion of the reference mark exists cannot be known.
While a conventional technique such as the one described in Japanese Patent Laid-Open No. 2002-79676 sufficiently satisfied the image quality requirements in the past, more accurate alignment becomes necessary in order to satisfy the image quality demanded now and in the future.